This is a note to let you know that I've just added the patch titled

x86/asm: Move 'status' from thread_struct to thread_info

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: x86asm_Move_status_from_thread_struct_to_thread_info.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

Subject: x86/asm: Move 'status' from thread_struct to thread_info From: Andy Lutomirski luto@kernel.org Date: Sun Jan 28 10:38:50 2018 -0800

From: Andy Lutomirski luto@kernel.org

commit 37a8f7c38339b22b69876d6f5a0ab851565284e3

The TS_COMPAT bit is very hot and is accessed from code paths that mostly also touch thread_info::flags. Move it into struct thread_info to improve cache locality.

The only reason it was in thread_struct is that there was a brief period during which arch-specific fields were not allowed in struct thread_info.

Linus suggested further changing:

ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);

to:

if (unlikely(ti->status & (TS_COMPAT|TS_I386_REGS_POKED))) ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED);

on the theory that frequently dirtying the cacheline even in pure 64-bit code that never needs to modify status hurts performance. That could be a reasonable followup patch, but I suspect it matters less on top of this patch.

Suggested-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Andy Lutomirski luto@kernel.org Signed-off-by: Thomas Gleixner tglx@linutronix.de Reviewed-by: Ingo Molnar mingo@kernel.org Acked-by: Linus Torvalds torvalds@linux-foundation.org Cc: Borislav Petkov bp@alien8.de Cc: Kernel Hardening kernel-hardening@lists.openwall.com Link: https://lkml.kernel.org/r/03148bcc1b217100e6e8ecf6a5468c45cf4304b6.151716446... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- arch/x86/entry/common.c | 4 ++-- arch/x86/include/asm/processor.h | 2 -- arch/x86/include/asm/syscall.h | 6 +++--- arch/x86/include/asm/thread_info.h | 3 ++- arch/x86/kernel/process_64.c | 4 ++-- arch/x86/kernel/ptrace.c | 2 +- arch/x86/kernel/signal.c | 2 +- 7 files changed, 11 insertions(+), 12 deletions(-)

--- a/arch/x86/entry/common.c +++ b/arch/x86/entry/common.c @@ -208,7 +208,7 @@ __visible inline void prepare_exit_to_us * special case only applies after poking regs and before the * very next return to user mode. */ - current->thread.status &= ~(TS_COMPAT|TS_I386_REGS_POKED); + ti->status &= ~(TS_COMPAT|TS_I386_REGS_POKED); #endif

user_enter_irqoff(); @@ -306,7 +306,7 @@ static __always_inline void do_syscall_3 unsigned int nr = (unsigned int)regs->orig_ax;

#ifdef CONFIG_IA32_EMULATION - current->thread.status |= TS_COMPAT; + ti->status |= TS_COMPAT; #endif

if (READ_ONCE(ti->flags) & _TIF_WORK_SYSCALL_ENTRY) { --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -459,8 +459,6 @@ struct thread_struct { unsigned short gsindex; #endif

- u32 status; /* thread synchronous flags */ - #ifdef CONFIG_X86_64 unsigned long fsbase; unsigned long gsbase; --- a/arch/x86/include/asm/syscall.h +++ b/arch/x86/include/asm/syscall.h @@ -60,7 +60,7 @@ static inline long syscall_get_error(str * TS_COMPAT is set for 32-bit syscall entries and then * remains set until we return to user mode. */ - if (task->thread.status & (TS_COMPAT|TS_I386_REGS_POKED)) + if (task->thread_info.status & (TS_COMPAT|TS_I386_REGS_POKED)) /* * Sign-extend the value so (int)-EFOO becomes (long)-EFOO * and will match correctly in comparisons. @@ -116,7 +116,7 @@ static inline void syscall_get_arguments unsigned long *args) { # ifdef CONFIG_IA32_EMULATION - if (task->thread.status & TS_COMPAT) + if (task->thread_info.status & TS_COMPAT) switch (i) { case 0: if (!n--) break; @@ -177,7 +177,7 @@ static inline void syscall_set_arguments const unsigned long *args) { # ifdef CONFIG_IA32_EMULATION - if (task->thread.status & TS_COMPAT) + if (task->thread_info.status & TS_COMPAT) switch (i) { case 0: if (!n--) break; --- a/arch/x86/include/asm/thread_info.h +++ b/arch/x86/include/asm/thread_info.h @@ -55,6 +55,7 @@ struct task_struct;

struct thread_info { unsigned long flags; /* low level flags */ + u32 status; /* thread synchronous flags */ };

#define INIT_THREAD_INFO(tsk) \ @@ -221,7 +222,7 @@ static inline int arch_within_stack_fram #define in_ia32_syscall() true #else #define in_ia32_syscall() (IS_ENABLED(CONFIG_IA32_EMULATION) && \ - current->thread.status & TS_COMPAT) + current_thread_info()->status & TS_COMPAT) #endif

/* --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -557,7 +557,7 @@ static void __set_personality_x32(void) * Pretend to come from a x32 execve. */ task_pt_regs(current)->orig_ax = __NR_x32_execve | __X32_SYSCALL_BIT; - current->thread.status &= ~TS_COMPAT; + current_thread_info()->status &= ~TS_COMPAT; #endif }

@@ -571,7 +571,7 @@ static void __set_personality_ia32(void) current->personality |= force_personality32; /* Prepare the first "return" to user space */ task_pt_regs(current)->orig_ax = __NR_ia32_execve; - current->thread.status |= TS_COMPAT; + current_thread_info()->status |= TS_COMPAT; #endif }

--- a/arch/x86/kernel/ptrace.c +++ b/arch/x86/kernel/ptrace.c @@ -935,7 +935,7 @@ static int putreg32(struct task_struct * */ regs->orig_ax = value; if (syscall_get_nr(child, regs) >= 0) - child->thread.status |= TS_I386_REGS_POKED; + child->thread_info.status |= TS_I386_REGS_POKED; break;

case offsetof(struct user32, regs.eflags): --- a/arch/x86/kernel/signal.c +++ b/arch/x86/kernel/signal.c @@ -787,7 +787,7 @@ static inline unsigned long get_nr_resta * than the tracee. */ #ifdef CONFIG_IA32_EMULATION - if (current->thread.status & (TS_COMPAT|TS_I386_REGS_POKED)) + if (current_thread_info()->status & (TS_COMPAT|TS_I386_REGS_POKED)) return __NR_ia32_restart_syscall; #endif #ifdef CONFIG_X86_X32_ABI

Patches currently in stable-queue which might be from torvalds@linux-foundation.org are

queue-4.14/objtool_Add_support_for_alternatives_at_the_end_of_a_section.patch queue-4.14/x86pti_Do_not_enable_PTI_on_CPUs_which_are_not_vulnerable_to_Meltdown.patch queue-4.14/x86_Introduce_barrier_nospec.patch queue-4.14/x86speculation_Use_Indirect_Branch_Prediction_Barrier_in_context_switch.patch queue-4.14/x86get_user_Use_pointer_masking_to_limit_speculation.patch queue-4.14/x86_Introduce___uaccess_begin_nospec()_and_uaccess_try_nospec.patch queue-4.14/x86cpufeature_Blacklist_SPEC_CTRLPRED_CMD_on_early_Spectre_v2_microcodes.patch queue-4.14/x86cpufeatures_Add_Intel_feature_bits_for_Speculation_Control.patch queue-4.14/x86paravirt_Remove_noreplace-paravirt_cmdline_option.patch queue-4.14/KVM_VMX_Make_indirect_call_speculation_safe.patch queue-4.14/x86msr_Add_definitions_for_new_speculation_control_MSRs.patch queue-4.14/x86alternative_Print_unadorned_pointers.patch queue-4.14/KVMVMX_Allow_direct_access_to_MSR_IA32_SPEC_CTRL.patch queue-4.14/x86cpufeatures_Add_CPUID_7_EDX_CPUID_leaf.patch queue-4.14/array_index_nospec_Sanitize_speculative_array_de-references.patch queue-4.14/Documentation_Document_array_index_nospec.patch queue-4.14/x86entry64_Remove_the_SYSCALL64_fast_path.patch queue-4.14/x86retpoline_Remove_the_esprsp_thunk.patch queue-4.14/x86bugs_Drop_one_mitigation_from_dmesg.patch queue-4.14/x86cpufeatures_Add_AMD_feature_bits_for_Speculation_Control.patch queue-4.14/scripts-faddr2line-fix-cross_compile-unset-error.patch queue-4.14/KVMSVM_Allow_direct_access_to_MSR_IA32_SPEC_CTRL.patch queue-4.14/x86asm_Move_status_from_thread_struct_to_thread_info.patch queue-4.14/KVMx86_Add_IBPB_support.patch queue-4.14/x86_Implement_array_index_mask_nospec.patch queue-4.14/KVMVMX_Emulate_MSR_IA32_ARCH_CAPABILITIES.patch queue-4.14/nl80211_Sanitize_array_index_in_parse_txq_params.patch queue-4.14/moduleretpoline_Warn_about_missing_retpoline_in_module.patch queue-4.14/x86speculation_Add_basic_IBPB_(Indirect_Branch_Prediction_Barrier)_support.patch queue-4.14/x86speculation_Simplify_indirect_branch_prediction_barrier().patch queue-4.14/x86nospec_Fix_header_guards_names.patch queue-4.14/KVM_x86_Make_indirect_calls_in_emulator_speculation_safe.patch queue-4.14/x86uaccess_Use___uaccess_begin_nospec()_and_uaccess_try_nospec.patch queue-4.14/x86entry64_Push_extra_regs_right_away.patch queue-4.14/x86usercopy_Replace_open_coded_stacclac_with___uaccess_begin_end.patch queue-4.14/vfs_fdtable_Prevent_bounds-check_bypass_via_speculative_execution.patch queue-4.14/x86retpoline_Simplify_vmexit_fill_RSB().patch queue-4.14/objtool_Warn_on_stripped_section_symbol.patch queue-4.14/x86spectre_Report_get_user_mitigation_for_spectre_v1.patch queue-4.14/x86cpufeatures_Clean_up_Spectre_v2_related_CPUID_flags.patch queue-4.14/x86syscall_Sanitize_syscall_table_de-references_under_speculation.patch queue-4.14/objtool_Improve_retpoline_alternative_handling.patch